Plasmid comparison. Here we applied one of the analysis available in the Blast2Network package  consisting in a comparison of plasmid gene content (see Methods for a concise description of the methodology). Values connecting nodes (plasmids) correspond to the percentage of shared genes with respect to the total number of genes of the two plasmids (Jaccard coefficient) and can be considered as a measure of relatedness in terms of evolutionary history (common ancestor) and horizontal transfers and recombination. After this analysis, two groups of plasmids emerged, that are connected through the edge between plasmids pBCNF5603 and pCP13. In the right group of plasmids we identified some VirR targets. The high similar gene content of some of the plasmids in that group may suggest a high rate of horizontal transfer/recombination between different strains, so raising the possibility of the transfer of the VirR targets. Moreover, the connection between the two groups can also suggest that transfers between the two groups of plasmids can happen.